Secure communication in the low-SNR regime

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33 Scopus citations


Secrecy capacity of a multiple-antenna wiretap channel is studied in the low signal-to-noise ratio (SNR) regime. Expressions for the first and second derivatives of the secrecy capacity with respect to SNR at SNR = 0 are derived. Transmission strategies required to achieve these derivatives are identified. In particular, it is shown that it is optimal in the low-SNR regime to transmit in the maximal-eigenvalue eigenspace of φ = H m d H m-N mN eh e d H e where H m and H e denote the channel matrices associated with the legitimate receiver and eavesdropper, respectively, and N m and N e are the noise variances at the receiver and eavesdropper, respectively. Energy efficiency is analyzed by finding the minimum bit energy required for secure and reliable communications, and the wideband slope. Increased bit energy requirements under secrecy constraints are quantified. Finally, the impact of fading is investigated, and the benefits of fading in terms of energy efficiency are shown.

Original languageEnglish (US)
Article number6155699
Pages (from-to)1114-1123
Number of pages10
JournalIEEE Transactions on Communications
Issue number4
StatePublished - Apr 2012


  • Energy efficiency
  • Gaussian channels
  • MIMO systems
  • energy per secret bit
  • fading channels
  • information-theoretic security
  • low-SNR regime
  • secrecy capacity

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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